[chromecast] Slew stream volume changes in StreamMixerAlsa.

chromecast/media/cma/backend/alsa/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
 import("//build/config/chromecast_build.gni")
 import("//chromecast/chromecast.gni")
 import("//media/media_options.gni")
 import("//testing/test.gni")
 
@@ skipping 37 matching lines @@
     "stream_mixer_alsa_input.h",
     "stream_mixer_alsa_input_impl.cc",
     "stream_mixer_alsa_input_impl.h",
   ]
 
   libs = [ "asound" ]
 
   deps = [
     ":alsa_features",
     ":audio_filter_includes",
+    ":slew_volume",
     "//base",
     "//chromecast/base",
     "//chromecast/media/cma/backend",
     "//chromecast/media/cma/base",
     "//chromecast/media/cma/decoder",
     "//chromecast/public/media",
     "//media",
     "//media:shared_memory_support",
   ]
 
@@ skipping 19 matching lines @@
     "audio_filter_factory.h",
     "audio_filter_interface.h",
   ]
 
   deps = [
     "//base",
     "//media",
   ]
 }
 
+source_set("slew_volume") {
+  sources = [
+    "slew_volume.cc",
+    "slew_volume.h",
+  ]
+  deps = [
+    "//base",
+    "//media",
+  ]
+}
+
 # GYP target: chromecast/media/media.gyp:chromecast_alsa_features
 buildflag_header("alsa_features") {
   header = "alsa_features.h"
 
   flags = [ "ALSA_MONOTONIC_RAW_TSTAMPS=$use_alsa_monotonic_raw_tstamps" ]
 }
 
 # GYP target: chromecast/media/media.gyp:cast_alsa_cma_backend_unittests
 test("cast_alsa_cma_backend_unittests") {
   sources = [
@@ skipping 25 matching lines @@
   public_deps = [
     ":alsa_cma_backend",
   ]
 
   deps = [
     "//base",
     "//media",
     "//testing/gmock",
   ]
 }